The present invention relates to the purification of organically modified surface active mineral particulates by air classification and, more specifically, the purification of organically modified surface active mineral particulates from gangue particulates by air classification based on the size and density of the organically modified surface active mineral particulates compared to the gangue particulates.
As used herein, the term “surface active minerals” (“SAM”) are minerals that have exchangeable cations located along the mineral surface. These cations act as charge balance for ionic substitutions that exist within the crystalline structure of the mineral. When reacted with certain cations, such as fatty cationic surfactants, a cation exchange reaction can take place where the new cationic moiety becomes ionically bound to the mineral surface. SAMS reacted with such cations (e.g., the fatty cationic surfactants) in this manner are, as used herein, termed “organically modified surface active minerals” (“OMSAM”). As used herein, a SAM may be a clay or a zeolite, and an OMSAM may be an organoclay or an organozeolite. Unless otherwise specified, the use of the term “SAM” refers to both clays and zeolites, and the term “OMSAM” refers to both organoclays and organozeolites.
The layer of ions of the hydrophilic SAM are exchanged for the organocations of the cationic surfactant causing the tail groups of the cationic surfactant to extend from the SAM, thereby generating an organophilic surface consisting of covalently linked organic moieties and forming an OMSAM. Crude mineral compositions or ore may contain desirable SAMs, as well as undesirable materials, referred to as gangue. As used in the present application, the term “gangue” refers to materials closely mixed with, or surrounding, the desired SAM material. Gangue may include, but is not limited to, amounts of quartz, calcite, chloride salts, and the like. In some cases, gangue may be a non-swellable material whereas the SAM may be either a non-swellable material (e.g., a zeolite) or a swellable material (e.g., an organoclay).
OMSAMs, such as organoclays, may be beneficially swellable in the presence of hydrocarbon fluids (e.g., oils) due to the reaction of the hydrophilic SAM, which is initially swellable in the presence of aqueous fluids, and the cationic surfactant. These organoclays may be used to remove oil from water, as well as a nucleating agent, for example. OMSAMs have wide applicability in a number of industries, ranging from use in oil-based treatment fluids in the oil and gas industry (e.g., as a viscosifying agent) and use in removing oil contamination in environmental cleanup operations, to use in forming cosmetics, lubricant grease formulations, paints, plastic materials, printing inks, polymer nanocomposites, and the like. Although the presence of gangue may be permitted in some such industry applications, it is generally preferred that gangue be minimized or eliminated completely to enhance the operability of the OMSAM. This may be particularly true in applications that permit only a small amount of the OMSAM to be included, such as in cosmetics applications) that require maximum swelling or oil absorption (e.g., by an organoclay). Moreover, gangue may appear in certain applications as a grit-like material, which is particularly disfavored in many applications, for example, the presence of a gritty material in paint is visually unpleasing, gritty materials may interfere and damage metal parts (e.g., bearings), and the like.
Forming substantially purified OMSAM having little or no gangue material mixed therewith is currently formed using a so-called wet slurry process. The wet slurry process involves treating crude mineral ore having desirable SAM materials and undesirable gangue materials with various water processes including washing, separating, drying, grinding, heating, sieving, and passing through an ion exchange columns to remove divalent cations and impurities. Each of these processes are water and energy intensive operations, and furthermore require significant operator time, equipment expense, equipment footprint space and infrastructure, and the like. Such processes additionally create considerable waste streams of water containing gangue and chemical byproducts (e.g., surfactants, salts, and the like) that must be safely disposed. Accordingly, substantially purified OMSAMs (i.e., those having mixed gangue therewith) are currently high-margin products that are expensive to produce and expensive to purchase, thereby driving up the costs of operations or products requiring them.